The ban, justified on grounds of cost and disruption, faces a legal challenge by transgender rights activists.
"This policy is a shameful slap in the face to people who put their
lives on the line everyday to defend our country..." said Jennifer Levi,
an official at Glad (GLBTQ Legal Advocates & Defenders), in a
statement.

"We are moving quickly with our plaintiffs to see that a court puts a
stop to this latest demonstration of President Trump playing politics
with people's lives."

Between 4,000 and 10,000 US active-duty and reserve service members are believed to be transgender.